If you have account with Tomcat, all requests to your site(s) are handled by tomcat, thus .htaccess doesn't work. If you want to use .htaccess on your site or just in particular directory, you need to request us to unmount this domain/directory from Tomcat via support ticket. Please note, java applications will not work in the unmounted site/directory.
If you are sure that this problem is not related to Tomcat mappings (for example you are on PHP hosting plan, or target directory is already unmounted from tomcat), then we suggest you to check that you don't have a .htaccess file in upper level directory, if that file exists, please either try to rename or remove it.